Support towers generally consist of legs or leg assemblies and a drive tube or a base beam typically arranged in a generally triangular configuration with a driven wheel at or towards each of the two lower corners of the frame or towards the ends of the base beam. A driving motor assembly that is typically called a centre drive is commonly mounted near the centre of the base beam and includes a motor and a reduction gearbox. The centre drive connects to the two wheel boxes that may each include a drive worm via rotatable drive shafts and couplings. The drive shafts and couplings are covered for safety and longevity using suitable covers and a wheel assembly is connected to a hub of each wheel box.
In one common arrangement of this nature the centre drive, drive shafts and couplings are all located on one side of the base beam and the wheel boxes that are driven by the drive shafts are located between the base beam and the wheels. The arrangement therefore provides a leg and wheel assembly having a significant width in the direction of movement of the support tower and that width impacts on, and possibly damages, the crop being irrigated. The arrangement may also act to widen the wheel track which may contribute to or exacerbate rutting resulting from water run-off.
The wheel box may not be attached directly to the base beam but rather to a swivel bracket that is in turn attached to the base beam. On the one hand this may allow the wheel to be swung through 90 degrees so that the machine is therefore towable in the direction of the water supply pipe from one centre pivot circle to another. On the other hand, a wheel mounted to a swivel bracket can easily be set at a slight angle to effect a toe-in adjustment so that the wheel tracks properly in a circular wheel track in the case of a centre pivot arrangement.
The centre drive is, in any event, exposed to all the elements in addition to water from the irrigator. Plant material may penetrate to the inside of drive shaft covers and could damage oil seals on the centre drive and/or wheel boxes.
In existing arrangements many of the components are exposed and therefore susceptible to theft or vandalism.
There is scope for improvement of the situation.
The preceding discussion of the background to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was part of the common general knowledge in the art as at the priority date of the application.